When we use UV radiation it isn’t blocked by anything and hits the bacteria directly. After about 15-20 minutes the DNA is too damaged to allow the bacteria to replicate and thrive. The UV radiation we receive is mostly blocked by the ozone layer so most of the energy isn’t enough to do enough damage. If it could do the type of damage you’re inquiring about, life wouldn’t be able to survive at all.

There really isn’t enough information in this question to answer properly. A glass of water on a table in Iceland will behave differently than a glass of water in the southern US which would act differently than a glass of water in Ecuador just from the different ambient temperatures alone.